Integrated circuits are usually powered by an external power supply that provides a suitable operating voltage. When an integrated circuit chip is powered up, the power supply voltage rises from zero volts to a specified direct current (DC) operating voltage. The time interval during the rise of the power supply voltage signal is referred to as a “power-on reset interval.” During the power-on reset interval all components of an integrated circuit chip must be placed into correctly initialized states so that the integrated circuit chip will function properly when the power supply voltage reaches its operating voltage.
In an integrated circuit system that utilizes a crystal oscillator the power-on reset interval must be extended until the crystal has “warmed up” and has begun to oscillate at the correct frequency. For this reason an integrated circuit with an oscillator system may have an “on-chip initialization circuit” that operates during the power-on reset interval. The on-chip initialization circuit is capable of operating with a power supply voltage signal that has not yet reached its proper operating voltage.
One such prior art on-chip initialization circuit is described in U.S. Pat. No. 6,160,428 issued on Dec. 12, 2000 to Ronald Pasqualini. The Pasqualini patent describes a trigger circuit that is capable of providing an initialization signal to the state-dependent elements (e.g., flip flop circuits) of an integrated circuit. The Pasqualini patent also describes a “warm up” counter 602 that is used to generate a required delay for a crystal oscillator to reach its correct operating frequency.
The Pasqualini patent also describes a method for testing the crystal “warm up” delay counter 602. The twenty four (24) bit delay counter 602 is divided into two twelve (12) bit sub-counters. The two sub-counters are tested by traversing only two (2) times 212 states (=213 states) (i.e., 8,192 states) as compared with traversing 224 states (˜16 million states) for a twenty four (24) bit counter. The sub-counter test method reduces the test time of the initialization counter by a factor of approximately two thousand (2,000). For example, for a fifty megaHertz (50 MHz) clock the test time would be reduced from thirty two hundredths of a second (0.32 sec) to one hundred sixty (160) microseconds sec).
The Pasqualini method requires the use of additional circuitry that must be added to facilitate the accelerated testing of the crystal “warm up” delay counter 602.
There is a need in the art for a system and method that is capable of providing efficient testing of an on-chip initialization circuit. In particular, there is a need in the art for a system and method that is capable of providing an automated testing procedure for an on-chip initialization circuit.
Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.
Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior uses, as well as to future uses, of such defined words and phrases.